Method of producing safety motion-picture positive-film strips



June 3, 1924.

C. A. ROTH METHOD OF PRODUCING SAFETY MOTION PICTURE POSITIVE FILM STRIPS DDUUUD LIGHT.

F Lam M s W a 7 n E. M m M n c a M ,c a M C M m H a n 2 a. m m u n w e c m A M w w 7 W M H P m a a r V n M 4 M E H Patented June 3, 1924.

UNITED STATES 1,496,325 PATENT OFFICE.

CHARLES A. ROTH. OF NE! YORK. N. Y.. ASSIGNOR TO POWERS PHOTO ENGRAV'ING COMPANY, A CORPORATION OF NEW YORK.

METHOD OF PRODUCING SAFETY MOTION-PICTURE POSITIVE-FILM STRIPS.

Application filed April 26.

To a]? whom it may concern Be it. known that 1. CHARLES A. Born. a citizen of the United States. residing in New York. in the county and State of New York, have invented certain new and useful 1m provements in Methods of Producing Safety Motion-Picture Positive-Film Strips. of which the following is a specification.

The invention relates to a safety cinema or motion picture film strip. or to other film strips for use in projecting machines, and more particularly the invention relates to a process of manufacturing such film strips as will render them practically fireproof in the ordinary projecting machine.

Additional objects and advantages of the invention will be set forth in part in connection with the description of the presentpreferred embodiment. or will be apparent herefrom. or may be learned by practice with the invention.

The invention consists in the novel steps, combinations or sequence of steps and processes herein shown and described.

The accompanying drawings. herein referred to and constituting a part hereof. illustrate certain of the steps in the process of producing a film of the kind above indicated or described. such drawings being of a. diagrammatic character, and serving together with the description to explain the principles of the invention.

Of the drawings Fig. 1 is a diagrammatic showing, with the part, more or less magnified and out of proportions of a section through a film prepared in accordance with the invention; and

Fig. 2 is a front view of a similar kind or character.

While I do not wish to be circumscribed in any manner by a statement of theory, it. a1ppears that the film of my invention has t ie pgoperty or capacity for quickly and uniformly distributing or dissipating heat, so that a portion of my film which is directly subjected to relatively intense heat. or an unusually long application of heat (such as would ignite ordinary film), will remain at a temperature well below the combustion point or temperature for the constituent. materials of the film. It is also probable that the film has relatively high heat reflecting capacity and a relatively low heat absorbing capacity.

The film of the present invention has the 1920. Serial N0. 376,615.

flexible carrying strip or base 2 of celluloid, and upon one. side thereof the usual lightsensitive. positive coating or emulsion 3 which carries the images or pictures. In making the positive film strip. this emulsion is exposed to the action of light under the usual negative strip (which latter strip has been exposed in the motion picture camera), and thereafter my film is developed and fixed in the usual, or in any adequate or suitable, manner.

Upon the oppositeside of the base or carrier strip 2 of my film strip there is imposed or spread throughout its extent a coating 1 of gelatine emulsion in a non-sensitized state. This second or back coating 1 is preferably of similar kind. consistency and thickness as the sensitive emulsion. This coating is preferably applied at the time of manufacture of the film strip. and under similar conditions with the light sensitive emulsion or layer 3. The back of the film strip, as used herein. refers to the side of the film strip which is toward the light.

In practice. also. the second or heat protective coating or layer 1 may be applied to the back of the film strip 2 after the development thereof. and after the strip is otherwise finished for projection. I regard it preferable, however, to apply the pro tec-tive layer 1 to the back of the film strip 2 at the same time with the light-sensitive layer 3.

With either manner of applying, the heat protective emulsion layer to the back of the film strip, a proper binder is used, such as acetone. as is well known in the art. The entire strip is treated with a hardening solution or other agent subsequent to the print ing and developing of the light sensitive surface. Various hardening agents may be employed so far as concerns certain features of the invention. The solution or other agent will be such as shall give the film strip a high protective resistance against the heat of the projection light.

The hardening and fire proofing solution which I prefer to use. and which has proved very efficacious in actual use, consists of a mixture of equal parts of five per cent solution of formaldehyde and of a two per cent solution of sodium bi-sulfite. The sodium hi-sulfitc solution not only in creases the fire. or heat resisting property of the film but also prevents the forled maldehyde from rendering the celluloid brittle and non-pliable. This treatment not only hardens the film while keeping it pliable, but also imparts to the film greatly increased heat distributing or dissipating properties or capacity, and increasesjits resistance to ignition or deflagration.

The portable types of projectors now in common use employ nitrogen tungsten lamps, and such a film is capable of resisting the intense heat developed from such lamps, even when used with powerful condensers. By actual tests I have proved that it is impossible to ignite a film so treated when subjected to the steady light of such lamps in a standard type of portable projector when the film strip has remained stationary in the film gate of the projector for-over one hour and subject during the entire time to the full action of the projecting light upon the single place in the film strip. 1

It has always been a serious problem to endeavor to secure a film strip which possesses the necessary or acceptable degree of flexibility or pliability, together with acceptable pictorial quality, and which is safe for use against fire risks in the type of projector referred to. One of the principal dangers in the use of such machines arises from the film strip being stopped, and the portion exposed at the film gate becoming over-heated, and igniting or deflagratin as a result of the stoppage of the film. be present invention avoids absolutely this risk, as the film remains intact and unaffected by the heat fora period far beyond any of the contingencies of film stoppage or arrest which might arise during the operation of the machine.

While I have described my invention as applied to a film strip, it will be found useful as applied to celluloid and other slides of inflammable material, such as are used in certain kinds of advertising and other picture exhibiting machines. I What I claim is: a

1. The process of producing a heat resisting motion picture film for use in a projector, comprising applying to the usual celluloid film having a light sensitive material on one side, a coating of gelatine on film having a light sensitive material on one side, acoating of gelatine on the other side, that is, the side toward the light of the projector. and then treating the film with a hardening and fircproofiiig solution containing formaldehyde and sodium bi-sulfite or their equivalents, whereby the heat from the light of the projector is dissipated and ignition of the film prevented even if".

the film stops for a substantial length of time.

In testimony whereof. I have signed my name to this specification.

CHARLES A. ROTH. 

